36 min read

Published on

December 22, 2023

Innovative Postharvest Preservation of Berries: 5 Key Strategies

Explore sustainable methods for postharvest preservation of berries, enhancing shelf life while ensuring eco-friendliness.

Xam Richie

In the pursuit of healthier, sustainable food systems, the postharvest preservation of berries stands as a critical challenge.

Berries, with their short shelf life, demand innovative solutions to extend their viability while maintaining nutritional value.

This article delves into sustainable postharvest technologies, exploring natural methods and eco-friendly storage techniques.

From leveraging the power of nature to employing cutting-edge solutions, we examine how these practices not only prolong berry shelf life but also align with environmental sustainability.

We will uncover the potential of these innovative and natural preservation methods, marking a significant stride toward sustainable berry consumption.

Main Findings

Berries are highly perishable, leading to significant food and economic losses.
Traditional postharvest protection techniques, often involving chemicals, can be harmful to human health and the environment.
Sustainable alternatives for postharvest protection of berries are being explored, including green chemical compounds (e.g., ozone, hydrogen peroxide), bioactive compounds (e.g., essential oils, plant extracts), and physical methods (e.g., controlled atmosphere, low temperature).
The use of nanotechnology and artificial intelligence is emerging in berry preservation, enhancing functionality and safety.
Implementing these sustainable methods at an industrial scale poses challenges, including scale-up and regulatory policies.

Introduction: Why Berry Preservation Matters

As the world's population approaches 8 billion, with an expected rise to 9.8 billion by 2050, there's an increasing demand for fresh, minimally processed foods, including berries.

This demand impacts the environment through issues like deforestation and contamination .

Additionally, the degradation of soils due to intensive agriculture and a rise in hunger rates further challenge food production and security .

Berries stand out for their health benefits.

They contain phytochemicals like flavonoids and phenolic acids, known for their anti-inflammatory and anticancer properties, and are linked to lower risks of chronic diseases .

These small, brightly colored, and highly perishable fruits come in various forms, like strawberries, blueberries, and many lesser-known types .

Major berry producers include China, the US, Mexico, Poland, and Germany, with global production reaching 89.10 million tons in 2021 .

Berries are consumed fresh, frozen, or processed into jams and juices.

However, preserving them is challenging as they're prone to spoilage and contamination, leading to economic losses and health risks like food poisoning .

Traditionally, physical and chemical methods, including pesticides, have been used to preserve berries .

Nowadays, there's a shift towards sustainable alternatives, with nanotechnology and artificial intelligence (AI) playing crucial roles.

Nanotechnology improves packaging by slowing spoilage and maintaining quality, while AI optimizes preservation processes and predicts shelf life, enhancing efficiency and reducing human error .

Common Reasons Why Berries Spoil Quickly

Globally, fruit losses, including berries, range between 25 to 50% of total production, with even ideal storage conditions extending shelf life only marginally .

Factors contributing to berry spoilage are multifaceted, encompassing physical, physiological, and microbiological aspects .

Physical damage, such as bruising, cuts, and temperature extremes, significantly impacts berries, often leading to aesthetic and quality degradation .

Managing these factors is vital for preserving berry integrity.

Strategies include careful harvesting, transportation, and storage, keeping in mind temperature and humidity controls .

Biochemically, berries undergo changes postharvest that affect their flavor, color, and texture.

These include sugar utilization, anthocyanin breakdown, and enzymatic activity, all of which contribute to a decrease in quality and shelf life .

Effective management of these processes is essential to retain the desirable attributes of berries.

Microbiologically, berries are susceptible to various pathogens like Botrytis cinerea and Colletotrichum spp., leading to diseases that compromise their integrity .

Prevention and control of these infections are critical, with an increasing focus on using natural and green chemical compounds for safer and more sustainable preservation methods .

Understanding the causes of postharvest losses and applying a combination of traditional and recent technologies are key to extending the shelf life and ensuring the safety and quality of berry fruits .

Traditional Methods vs. Sustainable Approaches in Berry Preservation

In the field of postharvest solutions for berry fruits , fungicides like azoxystrobin and pyrimethanil play a crucial role in combating fungal diseases such as B. cinerea and Colletotrichum spp.

Azoxystrobin works by halting mitochondrial respiration , while pyrimethanil targets essential amino acid biosynthesis and inactivates decay-causing enzymes .

Additionally, sulphur dioxide, a safe compound, is used in berries, particularly blueberries and grapes, to prevent rotting and browning by inhibiting enzyme activities in spoilage microorganisms .

Despite their effectiveness, concerns over environmental and health impacts, like neurotoxicity risks in neural cells from azoxystrobin , are driving research towards biological disease control methods .

Advanced Techniques for Postharvest Berry Preservation

Green Chemical Compounds: Eco-Friendly Solutions for Keeping Berries Fresh Longer

Ozone: A Powerful Ally in Berry Preservation

Ozone, known for its robust oxidizing properties, effectively combats postharvest diseases in berries, such as blackberries, blueberries, and raspberries .

It works by damaging fungal spores and bacterial cells, thus controlling diseases like grey mold and anthracnose .

Not only does ozone treatment delay senescence and ripening, but it also preserves nutritional value, flavor, and texture .

However, the concentration is critical, as highlighted in studies where varying ozone levels had different impacts on strawberry varieties like Camino Real and San Andreas .

Hydrogen Peroxide: Dual-Role in Protection and Signaling

H2O2, breaking down into reactive oxygen species, can cause cellular damage at high concentrations or trigger protective pathways at lower levels .

It's shown to reduce ethylene production in berries, thus slowing ripening and maintaining quality.

However, higher concentrations, such as 5%, can alter color and sensory properties, as observed in strawberries .

The appropriate concentration for H2O2 application varies and requires careful consideration to avoid impacting the sensory qualities of the fruit .

Peracetic Acid (PAA): Effective but Requires Caution

PAA is a strong oxidizing agent used as a sanitizer for berries.

While effective in reducing microorganism populations on berries' surface, its concentration must be carefully managed .

High concentrations can control diseases like B. cinerea but may also lead to undesirable changes in the berries, such as discoloration or texture alterations .

At lower concentrations, PAA does not significantly impact the quality parameters of berries .

Organic Acids: Enhancing Natural Qualities

Organic acids like citric, ascorbic, malic, acetic, and lactic acid are naturally found in fruits and are used to preserve berry quality .

These acids help prevent spoilage, reduce browning, and enhance the flavor and aroma of berry fruits.

They also play a role in maintaining the natural taste and promoting color retention in berries .

However, more research is needed to fully understand their impact on a larger scale and in various contexts.

Bioactive Compounds: Postharvest Preservation of berries

The application of bioactive compounds like essential oils (EOs) and plant extracts is revolutionizing the way we extend the shelf life of these perishable fruits.

Essential Oils (EOs)

EOs, known for their antimicrobial and antioxidant properties, play a pivotal role in protecting berries against decay, weight loss, and firmness loss, key factors in maintaining fruit quality .

For example, coatings enriched with cinnamon oil on blueberries have shown remarkable benefits in preserving quality parameters during storage .

The application of EOs varies in effectiveness based on factors like composition, concentration, and droplet size.

Studies have demonstrated that smaller droplet sizes in emulsions, such as with lemongrass oil, enhance antimicrobial activity and improve overall fruit preservation .

Furthermore, EOs can also boost the antioxidant capacity of berries, as seen in blueberries treated with cinnamon oil, which exhibited significantly lower levels of reactive oxygen species (ROS) .

Plant Extracts

Similarly, plant extracts are gaining traction in berry preservation.

These extracts, obtained from various plant parts through methods like solvent extraction, are employed either by dipping berries in a solution or spraying them directly .

Notable examples include the use of Prosopis juliflora leaf extract and avocado peel extract, which have shown promising results in extending the shelf life of strawberries and other berries by inhibiting microbial growth and enhancing antioxidant properties .

Other plant sources like lotus leaf and Aloe vera have also been explored for their antioxidant and antifungal capacities, demonstrating significant potential in berry preservation .

These natural extracts not only protect the fruit but can also enhance their flavor profiles, making them more appealing to consumers .

However, it's important to acknowledge the challenges in using these bioactive compounds.

The complex and variable composition of EOs and plant-derived products can make achieving standardized characteristics challenging .

Therefore, understanding their interactions and optimizing extraction processes are crucial for maximizing their efficacy in berry preservation.

Physical Methods

Controlled and Modified Atmospheres for Berry Longevity

Controlled Atmosphere (CA) and Modified Atmosphere Packaging (MAP) are key in extending berry shelf life.

CA involves controlling O2 and CO2 levels, which has been shown to maintain firmness, reduce weight loss, and preserve polyphenol content in berries .

MAP, on the other hand, adjusts the gas composition around berries, effectively slowing down their respiration rate and extending shelf life.

Specific gas mixtures are chosen based on the berry type, with a focus on low O2 and high CO2 environments .

Both CA and MAP are effective in preserving the quality of berries, but their effects can vary among different cultivars, necessitating careful optimization for each type .

Low-Temperature Storage: A Classic Approach

The storage of berries at low temperatures (around 0 °C and 90–95% RH) is a traditional method that effectively slows down ripening and reduces the rate of fungal growth .

While this method is widely used for berries like strawberries, raspberries, and blackberries, care must be taken to avoid freezing damage.

UV Irradiation and Pulsed Electric Fields: Innovative Technologies

UV irradiation and Pulsed Electric Fields (PEF) are emerging technologies in berry preservation.

UV irradiation, particularly in the UV-C range, is effective in microbial inactivation and stimulating the production of phytochemicals like anthocyanins .

PEF, involving short high-voltage pulses, helps in inactivating microorganisms and can enhance the texture and nutritional quality of berries .

These methods, however, need to be carefully controlled to prevent potential damage to the berries.

Cold Plasma and Ionizing Irradiation: Cutting-edge Methods

Cold Plasma (CP) and ionizing irradiation are other advanced techniques.

CP's antimicrobial properties help in maintaining the quality of berries and can stimulate the production of beneficial compounds like phenols .

Ionizing irradiation, meanwhile, extends shelf life by damaging the DNA of microorganisms, although it requires careful handling to avoid quality degradation .

Ultrasound Technology: A Gentle Approach

Ultrasound (US) technology is a gentle method that uses high-frequency sound waves to inactivate pathogens and improve berry quality.

It can enhance enzyme activity and nutrient diffusion in berries, though it should be combined with other treatments to maximize effectiveness .

Edible Coatings: A Sustainable Option

Edible coatings, made from biopolymers like chitosan, sodium alginate, cellulose, and pectin, offer an eco-friendly alternative to synthetic films.

These coatings help in reducing respiration rate, water loss, and can be enriched with active ingredients like antimicrobials and antioxidants .

Additionally, formulations containing prebiotics have shown to enhance the antioxidant properties and extend the shelf life of coated fruits .

Biocontrol Agents: Nature's Protectors

Biocontrol, using bacteria, yeasts, fungi, or their by-products, is increasingly popular for berry preservation .

BCAs combat spoilage by competing for space and nutrients, inhibiting pathogen growth through secondary metabolites like volatile organic compounds (VOCs) and activating plant defenses .

Their effectiveness varies across different environments, but they're especially beneficial for extending berry shelf life without environmental or health risks .

For example, Bacillus species in blackberries can reduce soft rot by up to 40% through various mechanisms, including the production of surfactin, initurin A, and VOCs .

Biocontrol is dynamic, requiring careful in vivo testing to ensure efficacy and safety .

Molecular Tools: Tailoring Berry Longevity

Molecular biotechnology offers advanced solutions for extending berry shelf life by manipulating gene expression.

Antisense technology, which inhibits specific genes, and RNA interference (RNAi) are used to control fruit ripening and softening .

For instance, antisense technology targeting pectate lyase genes in strawberries resulted in firmer fruits with reduced gene expression .

Similarly, RNAi-silencing of genes involved in pectin modification improved fruit firmness .

CRISPR/Cas9 gene editing has also shown promise, with edited strawberry plants yielding firmer, less perishable fruits without significant changes in color, sweetness, or acidity .

These molecular approaches are promising for enhancing fruit quality, but considerations around safety, regulation, and environmental impact are crucial .

How AI is Revolutionizing Berry Preservation

AI systems analyze environmental data like temperature and humidity, crucial for maintaining berry quality.

These systems proactively adjust conditions to prevent quality degradation .

Additionally, AI predicts berry freshness by analyzing size, color, and sugar content, estimating shelf life and identifying potential issues .

Innovations like image-processing algorithms and electronic noses (E-noses) are also integral.

E-noses, simulating human smell, help in determining berry ripeness non-destructively .

However, AI's effectiveness depends on high-quality data and involves challenges like development costs, need for data science expertise, and regulatory considerations .

Despite these challenges, AI stands out as a powerful tool for ensuring optimal berry preservation conditions.

The Role of Nanotechnology in Extending Berry Shelf Life

Nanoparticle coatings, including those from natural sources like chitosan and cellulose nanocrystals, create barriers against moisture loss and pathogens, thereby extending shelf life .

These nanomaterials, ranging from 10 to 1000 nm in size, are employed in various forms, like nanospheres and nanocapsules, to carry antimicrobial agents effectively .

Nanoparticles loaded with antimicrobial substances, such as ε-polylysine, curcumin, and phenols, are particularly effective against a range of microorganisms, destabilizing their membranes and leading to cell content loss .

Additionally, nanotechnology-based edible coatings have been successfully used for berry preservation by encapsulating essential oils (EOs) .

Carbon dots (CDs), with their excellent fluorescence, stability, and biocompatibility, have gained interest for berry preservation due to their radical scavenging and antimicrobial activities, which contribute to delaying ripening and improving shelf life .

Moreover, carbon-based nanomaterials like nanotubes, integrated with polysaccharides and proteins, improve packaging by enhancing mechanical properties and creating effective barriers against moisture and oxygen .

Overcoming Challenges in Eco-Friendly Berry Preservation Techniques

The shift towards natural-based solutions like nanotechnology coatings and plant-derived antioxidants marks a growing trend in "Postharvest Preservation of Berries."

This movement addresses concerns about the environmental and health impacts of synthetic fungicides and chemicals, aiming to improve fruit quality and reduce postharvest losses, thereby enhancing food security .

However, challenges like higher production costs, need for specialized knowledge, and ensuring efficacy against various pathogens are significant hurdles .

Safety and compatibility with fruit requirements during transport and storage are crucial.

Scaling up these sustainable methods from laboratory to industrial scale poses a major challenge, alongside navigating complex regulatory frameworks .

Despite these issues, increasing research is bridging the gap between laboratory experiments and industrial applications, fostering the development and scaling of green alternatives for berry preservation.

This advancement is vital for tackling food security by preserving fruit quality and minimizing food waste.

Final Thoughts: The Future of Berry Preservation

Sustainable and eco-friendly strategies are gaining traction over traditional chemical methods.

These include cold storage, modified environment packaging, natural coatings, and the use of organic acids and essential oils.

Innovations in nanotechnology, like nanocomposite coatings and carbon dots (CDs), show promise in extending berry shelf life through smart packaging.

While these methods are more environmentally friendly, their effectiveness varies based on specific treatment conditions.

Additionally, molecular biology tools offer potential, though consumer acceptance of genetically modified foods remains a concern.

Collaborative efforts among scientists, industry, and government are key to successfully implementing these sustainable preservation techniques.

FAQs

How do you handle berries in postharvest?

Store berries in a cool and humid environment to maintain freshness. Sort and remove damaged or spoiled berries regularly. Handle gently to minimize bruising. Rinse berries just before consumption to avoid premature spoilage.

How do you preserve fresh berries?

Store fresh berries in the refrigerator to preserve their freshness. Avoid washing them until you are ready to consume them to prevent mold growth.

How long do berries last once harvested?

Berries typically last for about 3 to 7 days once harvested.

What is the postharvest treatment of fruit?

Postharvest treatment of fruit involves various techniques and processes to maintain the quality and extend the shelf life of fruits after they are harvested. These treatments aim to prevent spoilage, retain freshness, and enhance market value. Common postharvest treatments for fruits include cleaning, sorting, grading, washing, disinfection, waxing, cold storage, and controlled atmosphere storage.

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